1. Field of the Invention
The present invention relates to a layered structure of wire(s), a manufacturing method therefor, and an optical apparatus.
2. Description of the Related Art
A display employing a current driven organic EL (OLED: Organic Light Emitting Diode) device which acts as a light emitting diode has attracted attention as an alternative to a CRT or LCD.
In an optical element in an organic EL display, layered structure of wire(s) used as power supply lines must be highly reliable; specifically, it must have a lower resistance and be resistant to whiskers/hillocks, electromigration and stress migration. For reducing a resistance, a low-resistance metal such as aluminum is used as a wiring material.
A protective layer made of a refractory metal such as molybdenum may be formed on a wiring made of a low-resistance metal such as aluminum to improve resistance to whiskers/hillocks. Furthermore, resistance to electromigration may be improved by using an aluminum alloy containing at least one of lanthanoide series such as neodymium as a wiring material.
A layered structure of wire(s) employed in an organic EL must have a particularly lower resistance for preventing voltage drop. However, when using an aluminum alloy containing neodymium as a wiring material, the layered structure of wire(s) exhibits a higher specific resistance than that made of aluminum alone. Furthermore, forming a protective layer made of molybdenum may lead to a higher specific resistance.
Furthermore, when coating a layered structure of wire(s) made of a low-resistance metal with a protective layer made of a refractory-temperature metal, adherence between these layers may be deteriorated and a contact resistance may be undesirably increased. In particular, when a lattice type of the refractory metal is different form that of the low resistance metal, these layers cannot be matched, resulting in delamination. When forming a layered structure of wire(s) on an amorphous substrate, each layer exhibits a random crystal orientation so that interlayer adherence may be more seriously reduced.